The incident happened a few hours after the center was evacuated following a call to a Seattle television station saying there was a bomb in the courthouse.

The white powder was discovered about 2:20 p.m., Ohashi said. The man who found it immediately called 911, and when the Fire Department arrived firefighters isolated the substance and the people involved.

“The person who had the greatest exposure is being monitored, and there are no reports of any symptoms at this point,” Ohashi said about 5:15 p.m.

King County sheriff’s deputies also responded because the center is a county building. The powder analysis was expected to be complete late Wednesday night.

Tuesday morning, Kent police spokesman Paul Petersen said a man called the KING/5 news tipline saying there was an incendiary device at the Justice Center and that it was set to explode at 10 a.m.

The station reported the call to police. The building was evacuated and locked down, Maj. William Hayes of the Department of Adult and Juvenile Detention said.

At least eight bomb-sniffing dogs from the King County Sheriff’s Office, State Patrol, Port of Seattle and Department of Homeland Security searched the building, but found no sign of a bomb.

Jurors were told they could return at 1 p.m., and the building returned to normal operation until the package was discovered about an hour later.